You are given a perfect binary tree where all leaves are on the same level, and every parent has two children. The binary tree has the following definition:
struct Node { int val; Node *left; Node *right; Node *next; }
Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL
.
Initially, all next pointers are set to NULL
.
Example:
Input: {"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":null,"right":null,"val":4},"next":null,"right":{"$id":"4","left":null,"next":null,"right":null,"val":5},"val":2},"next":null,"right":{"$id":"5","left":{"$id":"6","left":null,"next":null,"right":null,"val":6},"next":null,"right":{"$id":"7","left":null,"next":null,"right":null,"val":7},"val":3},"val":1} Output: {"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":{"$id":"4","left":null,"next":{"$id":"5","left":null,"next":{"$id":"6","left":null,"next":null,"right":null,"val":7},"right":null,"val":6},"right":null,"val":5},"right":null,"val":4},"next":{"$id":"7","left":{"$ref":"5"},"next":null,"right":{"$ref":"6"},"val":3},"right":{"$ref":"4"},"val":2},"next":null,"right":{"$ref":"7"},"val":1} Explanation: Given the above perfect binary tree (Figure A), your function should populate each next pointer to point to its next right node, just like in Figure B.
Note:
- You may only use constant extra space.
- Recursive approach is fine, implicit stack space does not count as extra space for this problem.
1 /* 2 // Definition for a Node. 3 class Node { 4 public int val; 5 public Node left; 6 public Node right; 7 public Node next; 8 9 public Node() {} 10 11 public Node(int _val,Node _left,Node _right,Node _next) { 12 val = _val; 13 left = _left; 14 right = _right; 15 next = _next; 16 } 17 }; 18 */ 19 class Solution { 20 public Node connect(Node root) { 21 if (root == null) { 22 return null; 23 } 24 25 if (root.left != null) { 26 root.left.next = root.right; 27 if (root.next != null) { 28 root.right.next = root.next.left; 29 } 30 } 31 connect(root.left); 32 connect(root.right); 33 return root; 34 } 35 }